1. Field of the Invention
The present invention relates to a system for identifying freehand drawings such as characters and symbols, more specifically, the present invention relates to a freehand curve-drawing identifying system which inputs a fuzzy curve as fuzzy curve data involving vagueness in drawing, compares a curve sample model in which the input fuzzy curve data is divided into a plurality of segments with a fuzzy reference model as a reference pattern to discriminate a pattern of the input curve, and recognizes a pattern of the entire freehand curve from the segments.
2. Description of the Related Art
In recent years, a system so called a pen computer and the like, i.e. a computer system having as an input and output unit a pen and tablet system with a display unit has been highlighted. Such a pen computer system comprises, for example, a computer, a tablet with display connected to the computer and an input pen for input operation connected to the tablet. In this case, the tablet with display serves both as a display unit of an output unit of the computer and as an input unit of the computer.
In systems using such freehand input and in application programs executed by such systems, pen-input data by a drawer is recognized within the computer. For this reason, a curve-drawing data input by freehand pen must be recognized and determined within the computer.
Data input by pen on the tablet is generally given as a series of dots sampled at regular intervals of time. Accordingly, a spline interpolation technique is used to suitably interpolate to the sequence of dots so as to be capable of handling theoretically as a continuous curve.
As a conventional spline interpolation technique to obtain an interpolation curve from a given series of dots, combination coefficient of basis function is obtained based on coordinate data of each given point so as to express that the spline curve passes through these points. Then, a control polygon of the spline curve is obtained and finally the interpolation curve is obtained.
For example, in case of a cubic spline curve, a spline curve is obtained connected by cubic Bezier curves (which satisfies a so-called "C.sup.2 continuity" conditions, for example) which mutually and smoothly joins between passing points of the given interpolation point.
In order to determine characters or symbols from the spline-interpolated pattern data, a degree of matching between an input sample drawing and a predetermined reference drawing is obtained and a character or a symbol is recognized and determined corresponding to the reference drawing having the highest matching degree.
In such a conventional computer system, the spline interpolation process of sampled drawings is performed on the premise that the given series of dots are conclusive dots. However, the given input points often involve vague points and points positions of which are not rigorously correct. Nevertheless, the conventional system takes no account of cases where vague points and points, positions of which are not correct are involved in the given series of dots.
Further, not only the sampled drawings but also the reference drawings are processed as-certain conclusive data. As a result, the information associated with the degree of matching is obtained as mere conclusive information.
Accordingly, it is extremely difficult for the conventional system to perform the recognition process reflecting the intention of the drawer by suitably evaluating the vagueness from the input series of dots which may involve the vague points and points positions of which are not correct.
In order to solve this problem, the inventors of the present application have filed a Japanese Patent Application Tokuganhei 4-157573 with the Japanese Patent Office, which proposes a pattern recognition method and apparatus therefor capable of performing the pattern recognition reflecting the intention of the drawer by suitably evaluating vague elements from the input information.
According to this pattern recognition method and apparatus therefor, an input sampled drawing is expressed by fuzzy spline curves involving vagueness of the input sampled drawing. This system obtains predetermined number of fuzzy-expressed representative point information associated with the sampled drawing and predetermined number of fuzzy-expressed representative point information associated with the reference drawing in one-to-one correspondence with the representative points of the sampled drawing. Then, the system obtains interval truth values of the entire curve drawing from interval truth values of degree of matching between corresponding pairs of the representative point information of the sampled drawing and the representative point information of the reference drawing. Finally, the system determines the degree of matching of the entire curve drawing.
However, it is difficult to process huge data instantaneously from a view point of limited processing capability of an inference processing system when a freehand drawing intended by the drawer is inferred, discriminated and recognized from curve information of the input sampled drawing expressed by the fuzzy spline curves involving vagueness.